Access Control Lists

An access control list, ACL, in a computer file system refers to a list of permissions accompanying to an object. The purpose of an ACL is to grant permission/limit access of users and system processes to objects. Each entry in an ACL specifies the subject and operation. For example, if a file has an ACL that contains (Ben, update), this would grant Ben the permission to edit the file. When a subject requests an operation on an object in an ACL-based security model, the operating system will search for an applicable entry in the ACL to determine if the requested operation is authorized. A key issue in the definition of any ACL-based security model is determining how access control lists are edited, which refers to the users and processes that are granted permissions access ACL-modification. A filesystem ACL is a data structure containing entries that specify individual user or group rights to specific system objects such as programs, processes or files. The privileges or permissions determine specific access rights, such as whether a user is able to read from, write to, or execute an object. In some implementations, an ACE can control whether a user or group of users is permitted to edit the ACL on an object.

Resources: http://en.wikipedia.org/wiki/Access_control_list